The present invention relates to a novel organic boron compound, a process for production thereof and an organic (electro-)luminescence device using the organic boron compound.
An organic luminescence device generally comprises a pair of electrodes (comprising an anode and a cathode) and a film comprising a fluorescent organic compound disposed between the electrodes. Into the organic compound layer (film), holes and electrons are injected from the anode and the cathode, respectively, thus forming excitons of the fluorescent organic compound. When the excitons are returned to ground state, the organic luminescence device emits light or causes luminescence.
According to a study by Eastman Kodak Co. (xe2x80x9cAppl. Phys. Lett.xe2x80x9d, vol. 51, pp. 913-(1987)), it has been reported that a function-separation type organic luminescence layer comprising mutually laminated two layers including a layer of an aluminum quinolinol complex (as an electron transporting and luminescent material) and a layer of a triphenylamine derivative (as a hole transporting material) causes luminescence at a luminance (brightness) of ca. 1,000 cd/m2 under application of a voltage of ca. 10 volts. This is also reported in, e.g., U.S. Pat. Nos. 4,539,507; 4,720,432 and 4,885,211.
Further, by changing species of the fluorescent organic compound, it is possible to effect luminescence over broad wavelength regions ranging from an ultraviolet region to an infrared region. In this regard, various compounds have been extensively studied in recent years. Such compounds have been proposed in, e.g., U.S. Pat. Nos. 5,151,629, 5,409,783 and 5,382,477, and Japanese Laid-Open Patent Applications (JP-A) 2-247278, JP-A 3-255190, JP-A 5-202356, JP-A 9-202878 and JP-A 9-227576.
In addition to the above-mentioned organic luminescence devices using low-molecular weight materials, an organic luminescence device using a conjugated polymer has been reported by a research group of Cambridge University (xe2x80x9cNaturexe2x80x9d, vol. 347, pp. 539-(1990)). According to this report, a single layer of polyphenylenevinylene (PPV) is formed through a wet-coating process and luminescence from the single layer is confirmed. Such an organic luminescence device using a conjugated polymer has also been proposed by, e.g., U.S. Pat. Nos. 5,247,190, 5,514,878 and 5,672,678, JP-A 4-145192, and JP-A 5-247460.
As described above, recent progress in organic luminescence devices is noticeable, and the resultant organic luminescence devices are characterized by high luminance (brightness) under application of a low voltage, various (light-) emission wavelengths, high-speed responsiveness, small thickness and light weight, thus suggesting a possibility of wide applications.
However, the above-described organic luminescence devices are still required to effect light output (emission) at a higher luminance and/or a higher conversion efficiency in the present state. These organic luminescence devices are also still insufficient in terms of durability such that the devices are liable to be changed in their properties with time when used for a long period or liable to be deteriorated by the influence of ambient air containing oxygen or of humidity.
Further, as electron-injecting materials, there have been known: oxadiazole derivatives (JP-A 2-216791, JP-A 4-363891, etc.) and triazine derivatives (JP-A 7-41759, JP-A 7-90260, etc.). When used in an organic luminescence device, however, such an electron-injecting material is not fully satisfactory regarding provision of a stable layer or a sufficient electron injection efficiency. The luminescence intensity or the life is not sufficient either.
A generic object of the present invention is to provide an improvement to the above-mentioned state of the art.
A more specific object of the present invention is to provide a novel organic boron compound and a process for production thereof.
Another object of the present invention is to provide an organic luminescence device capable of high luminance light emission at a high efficiency while exhibiting a long life.
Another object of the present invention is to provide an organic luminescence device capable of emitting a diversity of luminescence wavelengths and exhibiting various luminescence hues with a very excellent durability.
A further object of the present invention is to provide an organic luminescence device, which can be produced easily and be relatively inexpensive.
According to the present invention, there is provided an organic boron compound represented by formula (1) below: 
wherein Ar1 denotes an optionally substituted aryl group or heterocyclic group; R1-R11 independently denote hydrogen, halogen, alkyl, alkenyl, amino, alkoxy, formyl, nitrile, aroyl, alkyloyl, aryl, aralkyl or heterocyclic group, each optionally substituted with the proviso that an adjacent one or more pairs of R1-R11 can form a condensed ring.
According to the present invention, there is also provided a process for producing an organic boron compound of the above formula (1), comprising:
(A) a step of reacting a ketone compound X with a ketone compound Y or an aldehyde compound in the presence of ammonium chloride, and
(B) a step of reacting a product of the step (A) with an organic boric acid compound.
The present invention further provides an organic luminescence device, comprising: a pair of electrodes comprising an anode and a cathode, and a layer of organic compound disposed between the electrodes; wherein the organic compound layer comprises an organic boron compound of the above formula (1).
The organic boron compound of the present invention exhibits a strong fluorescence characteristic and is useful as a luminescent material for a luminescence device.
The process of the present invention allows easy production of the organic boron compound.
The organic boron compound of the present invention is useful for constituting an electron-transporting layer or/and a luminescence layer, and is also useful for constituting an electron-injecting layer.
The organic luminescence device of the present invention is characterized by its capability of having an extremely high-luminance luminescence at a low application voltage, excellent durability, and also the capability to emit luminescence of various hues. For example, the organic luminescence device can cause luminance of primary colors, red, blue and green, and is therefore promising as a display device. Further, the device can be produced generally through vacuum deposition or casting, so that a large-area device can be easily produced at a relatively low cost.